/* $OpenBSD: bn_mod.c,v 1.23 2025/05/10 05:54:38 tb Exp $ */ /* Includes code written by Lenka Fibikova <fibikova@exp-math.uni-essen.de> * for the OpenSSL project. */ /* ==================================================================== * Copyright (c) 1998-2000 The OpenSSL Project. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * 3. All advertising materials mentioning features or use of this * software must display the following acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit. (http://www.openssl.org/)" * * 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to * endorse or promote products derived from this software without * prior written permission. For written permission, please contact * openssl-core@openssl.org. * * 5. Products derived from this software may not be called "OpenSSL" * nor may "OpenSSL" appear in their names without prior written * permission of the OpenSSL Project. * * 6. Redistributions of any form whatsoever must retain the following * acknowledgment: * "This product includes software developed by the OpenSSL Project * for use in the OpenSSL Toolkit (http://www.openssl.org/)" * * THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY * EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. * ==================================================================== * * This product includes cryptographic software written by Eric Young * (eay@cryptsoft.com). This product includes software written by Tim * Hudson (tjh@cryptsoft.com). * */ /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com) * All rights reserved. * * This package is an SSL implementation written * by Eric Young (eay@cryptsoft.com). * The implementation was written so as to conform with Netscapes SSL. * * This library is free for commercial and non-commercial use as long as * the following conditions are aheared to. The following conditions * apply to all code found in this distribution, be it the RC4, RSA, * lhash, DES, etc., code; not just the SSL code. The SSL documentation * included with this distribution is covered by the same copyright terms * except that the holder is Tim Hudson (tjh@cryptsoft.com). * * Copyright remains Eric Young's, and as such any Copyright notices in * the code are not to be removed. * If this package is used in a product, Eric Young should be given attribution * as the author of the parts of the library used. * This can be in the form of a textual message at program startup or * in documentation (online or textual) provided with the package. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * "This product includes cryptographic software written by * Eric Young (eay@cryptsoft.com)" * The word 'cryptographic' can be left out if the rouines from the library * being used are not cryptographic related :-). * 4. If you include any Windows specific code (or a derivative thereof) from * the apps directory (application code) you must include an acknowledgement: * "This product includes software written by Tim Hudson (tjh@cryptsoft.com)" * * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * The licence and distribution terms for any publically available version or * derivative of this code cannot be changed. i.e. this code cannot simply be * copied and put under another distribution licence * [including the GNU Public Licence.] */ #include "bn_local.h" #include "err_local.h" int BN_mod_ct(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) { return BN_div_ct(NULL, r, a, m, ctx); } int BN_mod_nonct(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) { return BN_div_nonct(NULL, r, a, m, ctx); } /* * BN_nnmod() is like BN_mod(), but always returns a non-negative remainder * (that is 0 <= r < |m| always holds). If both a and m have the same sign then * the result is already non-negative. Otherwise, -|m| < r < 0, which needs to * be adjusted as r := r + |m|. This equates to r := |m| - |r|. */ int BN_nnmod(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!BN_mod_ct(r, a, m, ctx)) return 0; if (BN_is_negative(r)) return BN_usub(r, m, r); return 1; } LCRYPTO_ALIAS(BN_nnmod); int BN_mod_add(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!BN_add(r, a, b)) return 0; return BN_nnmod(r, r, m, ctx); } LCRYPTO_ALIAS(BN_mod_add); /* * BN_mod_add() variant that may only be used if both a and b are non-negative * and have already been reduced (less than m). */ int BN_mod_add_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!BN_uadd(r, a, b)) return 0; if (BN_ucmp(r, m) >= 0) return BN_usub(r, r, m); return 1; } LCRYPTO_ALIAS(BN_mod_add_quick); int BN_mod_sub(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!BN_sub(r, a, b)) return 0; return BN_nnmod(r, r, m, ctx); } LCRYPTO_ALIAS(BN_mod_sub); /* * BN_mod_sub() variant that may only be used if both a and b are non-negative * and have already been reduced (less than m). */ int BN_mod_sub_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (BN_ucmp(a, b) >= 0) return BN_usub(r, a, b); if (!BN_usub(r, b, a)) return 0; return BN_usub(r, m, r); } LCRYPTO_ALIAS(BN_mod_sub_quick); int BN_mod_mul(BIGNUM *r, const BIGNUM *a, const BIGNUM *b, const BIGNUM *m, BN_CTX *ctx) { BIGNUM *rr; int ret = 0; BN_CTX_start(ctx); if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); goto err; } rr = r; if (rr == a || rr == b) rr = BN_CTX_get(ctx); if (rr == NULL) goto err; if (a == b) { if (!BN_sqr(rr, a, ctx)) goto err; } else { if (!BN_mul(rr, a, b, ctx)) goto err; } if (!BN_nnmod(r, rr, m, ctx)) goto err; ret = 1; err: BN_CTX_end(ctx); return ret; } LCRYPTO_ALIAS(BN_mod_mul); int BN_mod_sqr(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) { return BN_mod_mul(r, a, a, m, ctx); } LCRYPTO_ALIAS(BN_mod_sqr); int BN_mod_lshift1(BIGNUM *r, const BIGNUM *a, const BIGNUM *m, BN_CTX *ctx) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!BN_lshift1(r, a)) return 0; return BN_nnmod(r, r, m, ctx); } LCRYPTO_ALIAS(BN_mod_lshift1); /* * BN_mod_lshift1() variant that may be used if a is non-negative * and has already been reduced (less than m). */ int BN_mod_lshift1_quick(BIGNUM *r, const BIGNUM *a, const BIGNUM *m) { if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!BN_lshift1(r, a)) return 0; if (BN_ucmp(r, m) >= 0) return BN_usub(r, r, m); return 1; } LCRYPTO_ALIAS(BN_mod_lshift1_quick); int BN_mod_lshift(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m, BN_CTX *ctx) { BIGNUM *abs_m; int ret = 0; BN_CTX_start(ctx); if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); goto err; } if (!BN_nnmod(r, a, m, ctx)) goto err; if (BN_is_negative(m)) { if ((abs_m = BN_CTX_get(ctx)) == NULL) goto err; if (!bn_copy(abs_m, m)) goto err; BN_set_negative(abs_m, 0); m = abs_m; } if (!BN_mod_lshift_quick(r, r, n, m)) goto err; ret = 1; err: BN_CTX_end(ctx); return ret; } LCRYPTO_ALIAS(BN_mod_lshift); /* * BN_mod_lshift() variant that may be used if a is non-negative * and has already been reduced (less than m). */ int BN_mod_lshift_quick(BIGNUM *r, const BIGNUM *a, int n, const BIGNUM *m) { int max_shift; if (r == m) { BNerror(BN_R_INVALID_ARGUMENT); return 0; } if (!bn_copy(r, a)) return 0; while (n > 0) { if ((max_shift = BN_num_bits(m) - BN_num_bits(r)) < 0) { BNerror(BN_R_INPUT_NOT_REDUCED); return 0; } if (max_shift == 0) max_shift = 1; if (max_shift > n) max_shift = n; if (!BN_lshift(r, r, max_shift)) return 0; n -= max_shift; if (BN_ucmp(r, m) >= 0) { if (!BN_usub(r, r, m)) return 0; } } return 1; } LCRYPTO_ALIAS(BN_mod_lshift_quick);
